Reversing switch for load tap changing transformer



Filed Sept. 7, 1956 H BAGUHN 2,947,837

A. REVERSING SWITCH FOR LOAD TAP CHANGING TRANSFORMER 2 Sheets-Sheet 1 49M K5: Whammy Aug. 2, 1960 A. H. BAGUHN 2,947,837

REVERSING SWITCH FOR LOAD TAP CHANGING TRANSFORMER Filed Sept. 7, 1956 2Sheets-Sheet 2 C I I Tl- REVERSING SWITCH FOR LOAD TAP CHANGINGTRANSFORMER Alfred H. Baguhn, West Allis, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Sept. 7, 1956, Ser. No. 608,576

4 Claims. (Cl. 200-92) This invention relates in general to step typevoltage regulating apparatus and in particular to an improved reversingswitch assembly for such apparatus.

Step type voltage regulating apparatus are used extensively inelectrical distribution systems where it is desired to maintain thevoltage of a circuit between predetermined limits. Most apparatus ofthis type comprises an exciting winding connected across the circuit tobe regulated, and a tapped series winding connected in series with thecircuit through a load tap changing mechanism. The load tap changingmechanism includes a tap changing switch having a plurality ofstationary contacts connected respectively to the taps on the serieswinding, and movable contacts which cooperate with the stationarycontacts to insert diiierent portions of the series windings in thecircuit to be regulated.

In order to employ the same series winding and tap changing mechanism toeffect a change in voltage both above and below normal, the load tapchanging mechanism usually includes a reversing switch assembly which isoperable to reverse the connections of the tapped winding of theregulator with respect to the circuit to be regulated. Most reversingswitches include a pair of contacts connected respectively to oppositeends of the series winding and a third contact member connected to asupply terminal of the regulator. In a first position of the reversingswitch one end of the series winding is connected to the supplyterminal, and in a second position of the switch the other end of theseries winding is connected to the terminal. The reversing switch thusresembles a single pole double throw switch.

In order to operate the reversing switch from one position to the otherwhen it is not carrying current, a camming arrangement is employedbetween the load tap changing mechanism and the reversing switchassembly which causes the reversing switch to move when the movablecontacts of the tap changing switch are at the zero tap position of theregulator.

The switching action of the reversing switch usually starts prior to theswitching of the movable contacts of the tap changer from the Zero tapposition to insure that the reversing switch is suitably positionedprior to completion of the tap changing operation to either side of thezero tap.

In known prior art apparatus of the above type no provision is made toreturn the reversing switch to its original starting position in theevent that a tap changing operation from the zero tap to an adjacent tapis started but not completed. For example, it often happens that inregulating the voltage of a load circuit the tap changer is on the zerotap position when the control circuit for the regulator calls for a tapchange. The motor which operates the tap changing mechanism is thenenergized and a tap changing operation is started which through acamming arrangement starts to move the reversing switch. If at some timeprior to the time that the movable contacts of the tap changer areactually moved, the tap hired States Patent changing motor isdeenergized by the control circuit because conditions in the loadcircuit have corrected themselves, the movable member of the reversingswitch is disposed somewhere between the two stationary contacts of thereversing switch. It is thus possible for areing to occur between themovable member and the stationary contacts of the reversing switch dueto the fact that a charge is built up on the series winding under theseconditions. This arcing results in radio and television interference inaddition to shortening the life of the reversing switch contacts.

In accordance with the present invention the above mentioneddisadvantages of prior art regulators are eliminated by providing areversing switch assembly in which the movable member of the switch iscaused to return to its initial position in the event the tap changingoperation from the zero tap is not completed.

It is therefore an object of the present invention to provide animproved reversing switch assembly for a step type voltage regulator.

A further object of the present invention is to provide in a step typevoltage regulator, a reversing switch assembly which returns the switchto its initial position in the event the switching operation is startedbut not completed.

Objects and advantages other than those mentioned above will be apparentfrom the following description when read in connection with the drawingsin which:

Fig. 1 is a diagrammatic illustration of a step type voltage regulatingapparatus;

Fig. 2 is a front view in elevation of the tap changing mechanism forthe step type regulator shown in Fig. 1;

Fig. 3 is a side view in elevation of the tap changing mechanism shownin Fig. 1;

Fig. 4 is an isometric view of the improved reversing switch assemblyshown in Figs. 2 and 3; and

Figs. 5, 6 and 7 illustrate the operation of the reversing switchassembly shown in Fig. 4.

Referring to the drawing and particularly to Fig. 1 the step regulatorillustrated therein comprises generally an exciting winding 11, a serieswinding 12 which is provided with a plurality of taps 13, a load tapchanging mechanism 14 for connecting various portions of winding 12 inthe circuit 15, and a reversing switch assembly 16 which operates toconnect either end 17 or end 18 of winding 12 to supply terminal 19 ofthe regulator.

As shown in Fig. l exciting winding 11 is adapted to be connected acrossa circuit to be regulated and series winding 12 is adapted to beconnected in series with the circuit to be regulated, the windings beinginductively related by means of a magnetic core 20. As is well known,the voltage of the circuit 15 is varied in steps by operation of theloadtap changing mechanism 14, the reversing switch assembly 16 of mechanism14, being employed to eifect variations in voltage either below or abovethe voltage supplied to exciting winding 11. While the illustratedembodiment shows the series winding 12 provided with taps, it should beunderstood that other suitable arrangements of the windings and tapsknown in the art may be employed with the improved reversing switchassembly 16, Fig. 1 being merely illustrative of one type of regulatingapparatus in which the present invention may be advantageously employed.

As shown in Figs. 2 and 3 the load tap changing mechanism 14 comprisesgenerally a dial type tap changing switch 22 and a quick break mechanism23. Tap changing switch 22 comprises a plurality of circumferentiallyspaced stationary contacts 24 and a pair of movable contacts 25a and25b. The stationary contacts 24 are mounted on an insulating panel 26and connected respectively to taps 13 of series winding 12, except forthe zero tap contact 24' which is connected to terminal 19 of theregulator.

ing relationship with respect to adjacent stationary contacts 24.Movable contacts 25 are connected to the circuit 15 through a midtapreactor 27.

Shaft 28 and movable contacts 25 are moved in steps with a snap actionby means of quick break mechanism 23. Quick break mechanism 23 comprisesgenerally a stationary index plate 29, a drive sprocket 30, an actuatingdisk 31, a detent means 32, and a latch device 33 which is fixedlyattached to the actuating disk 31 and engageable with a notch 34 in thestationary index plate 29. A crank like member 35 links the actuatingdisk 31 to the shaft 28 of tap changing switch 22.

Detent means 32 as shown comprises a pair of spring assemblies 36a and36b which are disposed between the drive sprocket 30 and the actuatingdisk 31. Each spring assembly 36 is connected between the drive sprocket30 and the actuating disk 31 by means of pin members 37. Quick breakmechanism 23 is driven by motor 38 through a chain 39, motor 38 beingenergized by means of a suitable condition responsive control circuit(not shown) associated with the circuit 15 connected to the loadterminals of the regulator.

The reversing switch assembly 16 comprises generally the reversingswitch 40 and a rocker assembly 41 to actuate switch 40 in accordancewith the movement of the tap changing switch 22. Reversing switch 40 asshown comprises three arcuately spaced fixed contacts 42, 43 and 44 anda pair of movable contacts 45. Contacts 42 and 44 are connectedrespectively to opposite ends of series winding :12 while contact 43 isconnected to source terminal 19 of the regulator. Movable contacts 45 ofswitch 40 operate in one position to connect end 17 of Winding 12 to thesupply terminal 19 of the regulator, and in the other position toconnect end 18 to the supply terminal 19.

Movable contacts 45 are fixedly attached to a shaft 46 which is suitablypositioned in insulating panel 26 on which stationary contacts 42, 43and 44 are suitably mounted. Contacts of the reversing switch 40 arepivoted from one position to the other by means of rocker assembly 41.Rocker assembly 41 shown in detail in Fig. 4 includes a member 50 whichis pivotally mounted on the vertical mounting panel 51 of the quickbreak mechanism 23, and a second member 52 which is attached to member50 by cross arms 53. Member 50 is provided with a recessed portion 54for receiving a cam pin 55 attached to the drive sprocket 30. Member 52is provided with as lot 56 for receiving a connecting pin 57 extendingfrom the movable portion of the reversing switch 40. Connecting pin 57functions to transmit the pivotal movement of assembly 41 to switch 40.Pin 55 is disposed on the sprocket 30 and functions with slot 54 as acam so that rocker assembly 41 is forced to pivot about a shaft 58 atthe start of the tap changing operation which is to move the movablecontacts 25 of the tap changer 22 from the zero tap position 24.

The reversing switch assembly 16 further includes means for causingrocker assembly 41 to return to either of tWo positions. This means asshown comprises a pair of spring assemblies 60. The spring assemblies 60are disposed diametrically opposite to each other with respect to theaxis of shaft 58 about which rocker assembly pivots. Each springassembly 60 comprises a spring guide tube 61 fixed at one end 62 to thedrive member 50, and provided with an elongated slot 63 for receiving apin element 64 secured to the mounting frame 51 of the quick breakmechanism 23. A compression spring 65 is disposed in the guide tube 61and acts between the drive member 56 and the pin element 64 to urgerocker assembly 41 to either of two extreme Positions when the cam pin55 attached to sprocket member 30 is not in engagement with the sideportion of the recess 54. If desired, additional springs may be disposedbetween the pin 64 and the outside and of the guide tube 61 to reducenoise during operation of the switch.

Assuming that the movable contacts 25 of the tap changing switch 22 areon the zero tap position 24 as shown in Figs. 1, 2 and 3, and that therocker assembly 41 is in the position shown in Figs. 2, 3 and, 5, theoperation of the regulating apparatus from the zero tap position issubstantially as follows. 7

Motor 38 is suitably energized by the control circuit (not shown) inresponse to a condition of circuit 15. Motor 38 is energized presumablyso that sprocket member 30 rotates counterclockwise as shown in Fig. 2.R0- tation of sprocket 30 causes cam pin 55 to move rocker assembly 41from the position shown in Fig. 5 to that shown in Fig. 6. Rotation ofsprocket 30 also causes spring assemblies 36a of detent means 32 tobecome biased. Energy from motor 38 is stored in biasing means 32because one end of assembly 36a is fixed to actuating disk 31 which iskept from moving by latch device 33, while the other end of assembly 36ais fixed to the sprocket 30. Latch device 33 is arranged so that it doesnot release until the rocker assembly 41 is substantially on the centerposition illustrated in Fig. 6.

If motor 38 remains energized so that the tap change from the zero tap24 is completed, rocker assembly 41 is moved to the position shown inFig. 7. The movable contacts 45 of reversing switch 40 are operated bymeans of pin 57, as shown in Fig. 4.

However, if motor 38 is deenergized prior to the time rocker assembly 41reaches an over center position which corresponds to the tripping timefor latch device 33, the detent means 32 returns the sprocket 30 towardits initial starting position, allowing the spring assemblies 60 to moverocker assembly 41 back to its original starting position.

It will thus be seen that the movable contacts 45 of the reversingswitch 40 are always in either of two extreme positions and cannot floatbetween the stationary contacts 42, 44 in the event a tap changingoperation is started but not completed.

While only one embodiment of the present invention has been illustratedand described it will be apparent to those skilled in the art thatmodification may be made therein without departing from the spirit ofthe invention or from the scope of the appended claims.

What is claimed is:

1. A reversing switch assembly for a quick break load tap changercomprising a two position reversing switch mounted on a shaft, a rockerassembly pivotally mounted on a frame of a tap changer, said rockerassembly being engageable at a point removed from its pivot by a pincarried in an are by a relatively slow moving motor driven element ofsaid tap changer to pivot said rocker assembly between positionscorresponding to the positions of-said reversing switch preparatorytothe quick break operation of the tap changing switch, said switch shaftengaged with said rocker assembly for transmitting the pivotal movementof said rocker assembly to said switch, and toggle means cooperatingwith opposite sides of said rocker assembly and urging said rockerassembly toward one of said positions after a predetermined pivotalmovement of said rocker assembly and urging said rocker assembly towardthe other of said positions to positively position said reversing switchindependently of the tap changer motor in the event that said motor isd'eenergized before said rocker assembly reaches said predeterminedposition.

2. A reversing switch assembly for a quick break load tap changercomprising a reversing switch mounted on a shaft and having twopositions each corresponding to one of two operating ranges of the tapchanger. a rocker as embly :pivotally mounted on a frame of the tapchanger, said rocker assembly being engageable at a point removed fromits pivot by a pin carried in an are by a relatively slow moving motordriven element of the tap changer to pivot said rocker assembly from afirst position corresponding to one of said ranges to a second positioncorresponding to the other of said ranges preparatory to the snapoperation of the tap changing switch from a Zero position into one ofsaid operating ranges, said switch shaft engaged with said rockerassembly for transmitting the pivotal movement of said rocker assemblyto said switch, and pair of spring means urging said rocker assembly toone of said positions to snap operate said reversing switch after apivotal movement of said rocker to a predetermined point and to returnsaid reversing switch to its initial position in event that the motor ofsaid tap changer is deenergized before said rocker assembly reaches saidpredetermined position.

3. A reversing switch assembly for a quick break load tap changingtransformer comprising a reversing switch having a pair of fixedcontacts and a movable contact mounted on a shaft for making contactwith one of said fixed contacts, a rocker assembly pivotally mounted ona frame of a tap changer, said rocker assembly having a recess removedfrom its pivot for receiving a pin carried by a relatively slow movingmotor driven element of said tap changer to pivot said rocker assembly,preparatory to a quick break movement of the tap changing switch, froman operating position associated with said movable contact of saidreversing switch to an operating position associated with one of saidfixed contacts, said switch shaft engaged with said rocker assembly fortransmitting the pivotal movement of said rocker assembly to saidreversing switch, and biasing means cooperating with 6 diametricallyopposed sides of said rocker assembly and urging said rocker assembly toone of its two positions to positively position said reversing switchindependently of the operation of said tap changer.

4. A reversing switch assembly for a quick break tap changingtransformer comprising a reversing switch having a pair of fixedcontacts and a movable contact mounted on a shaft, a rocker assemblypivotally mounted on a frame of the tap changer, said rocker assemblyhaving a recess removed from its pivot for receiving a pin carried by arelatively slow rotating motor driven element of the tap changer topivot said rocker from a first position to a second position, saidswitch shaft engaged with said rocker assembly for transmitting thepivotal movement of said rocker assembly to said reversing switch, and apair of springs cooperating with diametrically opposed sides of saidrocker to snap said reversing switch rapidly to one of said fixedcontacts after a predetermined pivotal movement of said rocker and torestore said reversing switch to the other of said fixed contacts inevent that the tap changing motor is deenergized before said rockerassembly completes said predetermined pivotal movement.

References Cited in the file of this patent UNITED STATES PATENTS2,177,109 Hill Oct. 24, 1939 2,253,183 Le Count Aug. 14, 1941 2,560,002Sealey July 10, 1951 2,679,563 Katsumata May 25, 1954 2,774,830 SealeyDec. 18, 1956 2,779,899 Lennox Jan. 29, 1957 2,791,648 Maloney May 7,1957

